Process for producing fluorinated dicyanobenzene

ABSTRACT

An object of the invention is to provide a process for industrially producing fluorinated dicyanobenzenes using tetrachlorodicyanobenzene as a raw material.  
     According to the present invention, fluorinated dicyanobenzene can be produced in a high yield by allowing tetrachlorodicyanobenzenes to react with a fluorinating agent in the presence of a non-protonic polar solvent in an amount of 0.1 to 3 times by mass based on the tetrachlorodicyanobenzene. Further, the above production can be conducted more efficiently by reacting while disintegrating or removing bulk solid matters.

CROSS REFERENCE OF RELATED APPLICATION

[0001] This application is an application filed under 35 U.S.C.§111(a)claiming benefit pursuant to 35 U.S.C. §119(e) of the filing date ofProvisional Application 60/256,915 filed on Dec. 21, 2000, pursuant to35 U.S.C. §111(b).

DETAILED DESCRIPTION OF THE INVENTION

[0002] 1. Technical Field

[0003] The present invention relates to a process for producingfluorinated dicyanobenzenes useful as an intermediate and raw materialfor preparation of medical and pharmaceutical products, agriculturalchemicals and polymers. Particularly, tetrafluoroterephthalonitrile isimportant as an intermediate for agricultural chemicals.

[0004] 2. Background Art

[0005] As a process for producing fluorinated dicyanobenzenesrepresented by the formula (2):

[0006] wherein m is an integer of 1 to 4, n is 0 or an integer of 1 to3, and m+n=4, a process for production of allowing a substituteddicyanobenzene to react with a fluorinating agent is known.

[0007] For example, JP-B-44-28493/1969 and Bull. Chem. Soc. Jpn, 40,688(1971) disclose a process for producing tetrafluoroterephthalonitrile by allowing tetrachloroterephthalonitrile to reactwith potassium fluoride in the absence of a solvent. This process,however, has an extremely high reaction temperature of 300° C. and aproblem of corrosion of a reaction device. Further, it has a complicatedprocess for isolating a product and a low yield of less than 80%, sothat it is difficult that this process is said to be an excellentprocess industrially.

[0008] JP-A-60-112751/1985 discloses a process for producingtetrafluorophthalonitrile by allowing tetrachloro phthalonitrile toreact with a fluorinating agent in the presence of a benzonitrilesolvent. The process has a high yield of from 90 to 92%, but a highreaction temperature of about 300° C. so that it has a problem ofcorrosion of a reaction device. Further, the process is required tocomplete the reaction for 10 hours or more and thereby this process ishardly said to be an advantageous process industrially.

[0009] In the meantime, JP-A-51-6940/1976 and U.S. Pat. No. 3975424disclose a process for preparing tetrafluoroterephthalonitrile byallowing tetrachloroterephthalonitrile to react with potassium fluoridein the presence of a polar solvent having a water content of not morethan 0.2%. This process has a low reaction temperature of 130° C. and anexcellent property such that the reaction is completed for a short timeof 5 hours. This process, however, has a low yield of at most 81%, andin the process, the solvent is used in an amount of 7.7 times by mass ormore-based on tetrachloroterephthalonitrile which is a raw material.Accordingly, in the case of carrying out the process industrially, it isexpected that its productivity is low and large amounts of wastes wouldbe discharged. The above prior arts, further, do not disclose a methodof recovering the solvent used in the reaction nor a reaction deviceemployed in carrying out the process industrially.

[0010] As described in the above, when carried out industrially,conventional processes for producing fluorinated dicyanobenzene haveproblems to be solved, such as its low yield and large amounts ofindustrial wastes.

OBJECT OF THE INVENTION

[0011] It is an object of the invention to provide a process forindustrially producing a fluorinated dicyanobenzene represented by theformula (2):

[0012] in the formula, m is an integer of 1 to 4, n is 0 or an integerof 1 to 3, and m+n=4, using, as a raw material,tetrachlorodicyanobenzene represented by the formula (1)

[0013] More specifically, in the processes for producing fluorinateddicyanobenzene by reacting tetrachlorodicyanobenzene with a fluorinatingagent, it is an object of the invention to provide a process forproducing a fluorinated dicyanobenzene in a high yield such that thereaction is carried out at a low temperature for a short time, which isunattained by conventional process.

[0014] Means to Solve the Problems

[0015] The present inventors have subjected tetracholo dicyanobenzene toreact with a fluorinating agent using a non-protonic polar solvent andexamined effect of the amount of the non-protonic polar solvent on thereaction rate and the yield of fluorinated dicyanobenzene.

[0016] In result, the present inventors have been now found thatdecreasing the non-protonic polar solvent amount to less than 3 times bymass per tetrachlorodicyanobenzene, unexpectedly, fluorinateddicyanobenzenes can be produced not only at an improved reaction rate,but also at a higher yield at a higher purity, as compared with usingthe amount more than 3 times by mass.

[0017] Up to this time, decreasing the solvent amount based on thetetrachlorodicyanobenzene, the yield of fluorinated dicyanobenzene isoccasionally lowered. The present inventors have found that decreasingthe amount of the non-protonic polar solvent to less than 3 times bymass based on the tetrachlorodicyanobenzene, the reaction mixture is wetpowdery or creamy, but not liquid, so that using conventional reactionvessels equipped with a stirrer, bulk solid matters are generated in thereaction mixture or adhered to the wall surface of the reaction vessel,and when the amounts thereof are increased, the yield of the aimedfluorinated dicyanobenzene is lowered. The inventors further have foundthat carrying out the reaction with disintegrating or removing the bulksolid matters, fluorinated dicyanobenzenes are preferably produced.

[0018] The present inventors have been accomplished the presentinvention on the basis of the above described investigation andfindings.

[0019] Namely, the present invention comprises the following items.

[0020] [1] The process for producing a fluorinated dicyanobenzenerepresented by the formula (2):

[0021] in the formula, m is an integer of 1 to 4, n is 0 or an integerof 1 to 3, and m+n=4, which process comprises allowing atetrachlorodicyanobenzene represented by the formula (1)

[0022] to react with a fluorinating agent in the presence of anon-protonic polar solvent in an amount of from 0.1 to 3 times by massbased on the tetrachlorodicyanobenzene.

[0023] [2] The process for producing a fluorinated dicyanobenzeneaccording to [1] wherein the non-protonic polar solvent is an organicsolvent comprising at least one selected from the group consisting ofN,N-dimethyl formamide, dimethyl sulfoxide and N-methyl-2-pyrrolidone.

[0024] [3] The process for producing a fluorinated dicyanobenzeneaccording to [1] wherein the non-protonic polar solvent is N,N-dimethylformamide.

[0025] [4] The process for producing a fluorinated dicyanobenzeneaccording to any one of [1] to [3] wherein the fluorinating agent is analkali metal fluoride or alkaline earth metal fluoride.

[0026] [5] The process for producing a fluorinated dicyanobenzeneaccording to [4] wherein the fluorinating agent is potassium fluoride.

[0027] [6] The process for producing a fluorinated dicyanobenzeneaccording to [5] wherein the potassium fluoride is prepared by a spraydrying method.

[0028] [7] The process for producing a fluorinated dicyanobenzeneaccording to claim [5] wherein the potassium fluoride has an averagebulk specific gravity of from 0.1 to 0.7 g/ml.

[0029] [8] The process for producing the fluorinated dicyanobenzeneaccording to any one of [1] to [7] wherein the fluorinateddicyanobenzene represented by the formula (2) is tetrafluorophthalonitrile, tetrafluoro isophthalonitrile or tetrafluoroterephthalonitrile.

[0030] [9] The process for producing the fluorinated dicyanobenzeneaccording to [8] wherein the fluorinated dicyanobenzene represented bythe formula (2) is tetrafluoro terephthalonitrile.

[0031] [10] The process for producing the fluorinated dicyanobenzene asdescribed in any one of [1] to [9], which process comprises carrying outthe reaction while disintegrating bulk solid matters contained in thereaction mixture and/or while removing bulk solid matters adhered to thewall inside the reaction vessel.

[0032] [11] The process for producing the fluorinated dicyanobenzene asdescribed in [10], wherein, in carrying out the reaction whiledisintegrating bulk solid matters contained in the reaction mixtureand/or while removing bulk solid matters adhered to the wall inside thereaction vessel, a mixing machine equipped with a ribbon-shaped and/orscrew-shaped stirrer is used.

[0033] [12] The process for producing the fluorinated dicyanobenzene asdescribed in [10], wherein, in carrying out the reaction whiledisintegrating bulk solid matters contained in the reaction mixtureand/or while removing bulk solid matters adhered to the wall inside thereaction vessel, any one device of a kneader mixer, internal mixer,muller mixer, crusher, ribbon-shaped mixer, vertical screw-shaped(planetary-shaped) mixer and rotary mixer is used.

[0034] [13] The process for producing the fluorinated dicyanobenzeneaccording to any one of [10] to [12], wherein the bulk solid matters arein an amount of not more than 10% by mass based on the total amount ofthe reaction mixture in carrying out the reaction.

[0035] [14] The process for producing the fluorinated dicyanobenzeneaccording to any one of [1] to [13], wherein the reaction temperature isfrom 80° C. to 200° C.

[0036] [15] The process for producing the fluorinated dicyanobenzene,which process comprises the steps of conducting the fluorinatingreaction with the process as described in any one of [1] to [14],thereafter cooling a reaction solution to lower than 60° C. and addingwater into the reaction solution to crystallize and deposit fluorinateddicyanobenzenes represented by the formula (2).

MODE OF CARRYING OUT THE INVENTION

[0037] The present invention will be further described in detailhereinafter.

[0038] The tetrachlorodicyanobenzene represented by the formula (1)

[0039] which is used as a raw material of the invention may include, forexample, tetrachloroterephthalonitrile, tetrachloroisophthalonitrile andtetrachloroorthophthalonitrile.

[0040] The reaction process of the present invention is carried out byfeeding tetrachlorodicyanobenzene, a non-protonic polar solvent in anamount of 0.1 to 3 times by mass based on the tetrachlorodicyanobenzeneand a fluorinating agent to a reaction vessel and heating at aprescribed temperature with stirring. After the reaction, the mixture iscrystallized and dried to prepare fluorinated dicyanobenzene of highpurity in a high yield.

[0041] The fluorinated dicyanobenzene, which is a product of the presentinvention, is a compound of the formula (2)

[0042] in which m is an integer of 1 to 4, n is 0 or an integer of 1 to3, and m+n=4, and may include, for example,trichlorofluorophthalonitrile, trichlorofluoroisophthalonitrile,trichlorofluoroterephthalonitrile, dichlorodifluorophthalonitrile,dichlorodifluoroisophthalonitrile, dichlorodifluoroterephthalonitrile,chlorotrifluorophthalonitrile, chlorotrifluoroisophthalonitrile,chlorotrifluoroterephtthalonitrile, tetrafluorophthalonitrile,tetrafluoroisophthalonitrile and tetrafluoroterephtalonitrile. Preferredexamples may include tetrafluorophthalonitrile,tetrafluoroisophthalonitrile, chlorotrifluoroisophthalonitrile andtetrafluoroterephthalonitrile. Further preferred examples may includetetrafluoroterephthalonitrile.

[0043] The fluorinated dicyanobenzene, which is a product of theinvention, can be mono-fluorine substituent, di-fluorine substituent,tri-fluorine substituent and tetra-fluorine substituent by regulatingthe amount of the fluorinating agent used in the reaction.

[0044] Examples of the fluorinating agent used in the present inventionmay include alkali metal fluorides or alkaline earth metal fluorides.Examples of the alkali metal fluorides may include potassium fluorides,sodium fluorides, cesium fluorides, rubidium fluorides and lithiumfluorides. Examples of the alkaline earth metal fluorides may includebarium fluorides and calcium fluorides. These fluorinating agents may beused alone or in combination of two or more. Among the above,commercially easily available potassium fluorides are speciallypreferred. Particularly, potassium fluorides prepared by the spraydrying method (available from Morita Chemicals Inc.) are preferred.Further, among them, potassium fluoride having an average bulk specificgravity of from 0.1 to 0.7 g/ml is effective because it has highreactivity.

[0045] The solvent used in the invention is not particularly limited aslong as it is a non-protonic polar solvent, and it may be used singly orin a mixture with other solvents. Appropriate examples of the solventmay include N,N-dimethylformamide (DMF), diethylformamide,dimethylsulfoxide (DMSO), dimethylsulfone (DMSO₂), sulforane,2-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone,dimethylacetoamide, and benzonitrile. Among them, N,N-dimethylformamide(DMF), dimethylsulfoxide (DMSO) and N-methyl-2-pyrrolidone arepreferred.

[0046] In the reaction of the present invention, the non-protonic polarsolvent is used in an amount of from 0.1 to 3 times by mass, preferably0.1 to 2 times by mass based on tetrachlorodicyanobenzene which is astarting material. When the non-protonic polar solvent is less than 0.1times by mass, the reaction rate is slow. When more than 3 times bymass, the yield of the resulting fluorinated dicyanobenzene is low.

[0047] The reaction of the present invention is carried out bythoroughly stirring the reaction mixture so that bulk solid matters arenot produced in the creamy or wet powdery reaction mixture. Duringcarrying out the reaction of the present invention, when the bulk solidmatters are produced in the reaction mixture, or produced and adhered tothe wall surface of the reaction vessel, it is preferred to carry outthe reaction while disintegrating or removing these bulk solid matters.In the reaction of the present invention, it is preferred that theamount of bulk solid matters contained in the reaction mixture oradhered to the wall surface of reaction vessel be smaller.

[0048] The term “bulk solid matters” used in the specification meanslarge solid matters, which are adhered to the inner wall of the reactor,or do not taken out and remained, after the liquid obtained by thereaction has been taken out from the reactor. The expression “removing”the bulk solid matters adhered to the wall surface of the reactionvessel means eliminating the bulk solid matters in the state fixed tothe wall surface, for example, from the adhered surface, separating,peeling, scratching away or disintegrating. More specifically, examplesof the procedure may include scratching away with a stirring blade andremoving with application of force.

[0049] The mixer used as the reactor of the present invention is notparticularly limited as long as it has a function of thoroughly stirringin such an extent that bulk solid matters are not produced in the creamyor wet powdery reaction mixture, or a function of disintegrating orremoving the bulk solid matters produced or adhered to the wall surfaceof the reaction vessel and also has a heating mechanism.

[0050] As described in the above, the reactor used in the invention hasno limitation as long as it has the function of disintegrating orremoving the bulk solid matters, and further for attaining such apurpose it is preferably a device equipped with a stirrer having aribbon-shaped or screw-shaped spiral blade.

[0051] Further, as the mixer having the heating mechanism suitable forthe reaction process of the present invention, for example, a mixingdevice usable for viscosity materials and a device capable of mixingbulk solid materials are effective.

[0052] Examples thereof are a mixer designed in such a structure thatthe gap between the wall surface and the stirring blade is narrow, and adevice of mixing while the screw revolves near the wall surface and alsorotates. Specific examples thereof may include a kneader mixer, internalmixer, muller mixer, crusher, ribbon-shaped mixer, vertical screw-shapedmixer (planetary-shaped) [Nauta-mixer (Trade Mark Hosokawa Micron CO.)or the like] and rotary mixer.

[0053] The fact that these mixers are effective in the reaction of thepresent invention means that it is unnecessary in the reaction of theinvention to enhance the stirring rate and make the whole reactionsystem uniform, as different from general reactions. This means that ifonly the mixing is conducted with disintegrating or removing bulk solidmatters in order to not produce large amounts of bulk solid matters, thereaction proceeds. That is, it indicates that the reaction system has toonly flow partly, but the whole does not need to be uniform. In usualreactions, even in solid-liquid reactions, it is a usual manner toconduct stirring so that the whole is uniform. Therefore, the reactionconditions of the present invention are those hardly expected fromcommon knowledge.

[0054] The amount of the bulk solid matters produced in the reactionmixture or adhered to the wall surface of the reaction vessel accordingto the present invention is preferably not higher than 10% by mass basedon the whole reaction mixture. When the amount is over 10% by mass, thereaction rate lowers, and further, the yield of fluorinateddicyanobenzene and the purity thereof lower.

[0055] In the case the reaction is continuously carried out with onereactor, if the amount of the bulk solid matters produced in thereaction mixture and adhered to the wall surface of the reaction vesselis not more than 10% by mass based on the whole reaction mixture, thereaction may be carried out with the bulk solid matters remained insidethe reactor and thereby particularly has no problems.

[0056] When the reaction mixture contains a large amount of water, thereis such a problem that the reaction rate lowers and the yield lowers, sothat the amount of the water is preferably smaller. Therefore, it ispreferred that the water amount in the raw materials including thefluorinating agent, solvent and terachlorodicyanobenzene be smaller.Further, it is effective for the reaction to plan on the device to avoidmoisture absorption or the like in feeding the raw materials, and topartly distill the solvent and then dehydrate after the feeding the rawmaterials. In some cases, it is also effective to distill and dehydrateby adding water-azeotropic other components.

[0057] In the present invention, the yield is increased by using thesolvent in an amount of less than 3 times by mass based on the rawmaterial tetrachlorodicyanobenzene. It is considered that one reason isbased on that the moisture contaminated in the reaction system is easilydepressed by decreasing the solvent amount used.

[0058] The reaction of the present invention is carried out at areaction temperature of from room temperature to 200° C., preferably 80to 200° C.

[0059] The reaction time varies depending to the reaction temperature orthe kind of the objective fluorinated dicyanobenzene, and may be usuallyless than 10 hours.

[0060] In the present invention, the reaction may be carried out in thepresence of a phase transfer catalyst. Examples of the phase transfercatalyst may include a quaternary phosphonium salt, quaternary ammoniumsalt, crown ether and polyalkylene glycol.

[0061] The fluorinated dicyanobenzene, which is the product of thepresent invention, can be isolated by, for example, crystallization,distillation, extraction, two-phase separation and sublimation. Amongthe methods, the crystallization of adding water into the reactionmixture after the reaction is effective. In the case of carrying out thecrystallization with adding water, it is preferred that the reactionmixture be cooled to lower than 60° C. before adding water because whenthe reaction solution temperature is high, the fluorinateddicyanobenzene product decomposes to decrease the yield and the purityof the resulting products. For example, in the preparation oftetrafluoroterephthalonitrile from tetrachloroterephthalonitrile andpotassium fluoride in the presence of a N,N-dimethylformamide solvent,tetrafluoroterephthalonitrile having high purity of not less than 97%can be easily isolated in such a way that the solution obtained afterthe reaction is cooled to lower than 60° C., then water is added in anamount of about 2.1 times by mass based on the used solvent to thesolution, and the water solution is subjected to crystallization andfiltration, and the resulting crystals are dried.

EFFECT OF THE INVENTION

[0062] According to the present invention, fluorinated dicyanobenzeneshaving high purity useful as an intermediate and raw material forpreparation of medical and pharmaceutical products, agriculturalchemicals and polymers can be produced in a high yield by industriallyprofitable methods.

Examples

[0063] The present invention will be described with reference to theexamples hereinafter.

[0064] <Analysis conditions>

[0065] The analysis conditions of liquid chromatography and gaschromatography employed in the examples are as follows.

[0066] (Analysis conditions of liquid chromatography) Device ShimazuLC-10 Column Shodex ODSpak F-511 (Particle diameter 5 μm, Size 4.6 mm(diameter) × 150 mm(length)) Eluting solution Acetonitrile/water = 40/60Flow rate 1 ml/min Detector UV (242 nm) Column temperature 50° C.Injection 5 μL

[0067] (Analysis conditions of gas chromatography) Device Agilent 6890Column Agilent J&W DB-1 (Size 30 m (length) × 0.53 mm(diameter) × 1.5 μm(film thickness)) Carrier Helium, 5.6 mL/min constant flow InjectionSplit (10:1), 1 μL, Inlet 300° C. Oven (1) 80° C. → 200° C. (5° C./min)(2) 200° C. → 290° C. (15° C./min) (3) 290° C. (5 mm) Detector FID 300°C. Internal standard substance o-dichlorobenzene Diluting solventAcetone

Example 1

[0068] Into a 1 L cylindrical flask, 210 g oftetrachloroterephthalonitrile having a purity of 98.35%, 205 g ofpotassium fluoride having an average bulk specific gravity of 0.5 g/mlprepared by the spray drying method and 475 g of N,N-dimethylformamidehaving a water content of 100 ppm as a solvent were charged, and whilestirring them with a large-sized stirrer having ribbon blade in anitrogen atmosphere, the temperature was elevated using an oil bathheated at 130° C. From the time at which the internal temperaturereached to 115° C., the reaction was continued for 4.5 hr. Thereafter,the reaction solution was cooled to 60° C., and transferred into a 2 Lround flask. The mass of bulk solid matters, which were adhered to thewall surface of the reactor during the reaction and remained after thetransfer of the reaction solution, was 42.75 g. (this mass correspondsto 4.8% of the all reaction solution mass). After the all amount of thereaction solution was transferred, 1018 g of water was introduced intothe reaction solution with stirring over 40 min, and thereby thepotassium chloride deposited were mostly dissolved and also crystals oftetrafluoroterephthalonitrile were deposited. The crystals wereseparated by a Nutsche funnel, and were washed with 400 g of water at40° C. When analyzed by liquid chromatography and evaluated, the totalamount of tetrafluorophthalonitrile present in the filtrate filtered andthe washing water was 0.21 g. (this amount corresponds to 0.14% of theyield based on tetrachloroterephthalonitrile) . The resulting crystalswere dried with a vacuum dryer at 60° C. to obtain 146.2 g of driedcrystals. When analyzed by gas chromatography, the crystals were foundto be tetrafluoroterephthalonitrile having a purity of 99.1%. The yieldbased on the tetrachloroterephthalonitrile was 93.2%.

Example 2

[0069] The procedure of Example 1 was repeated except the amount ofN,N-demethylformamide used was changed to 420 g. In result, 147.1 g ofdried crystals of tetrafluoroterephthalonitrile having a purity of 99.0%was prepared. The yield based on the tetrachloroterephthalonitrile was93.7%.

Example 3

[0070] The procedure of Example 1 was repeated except the amount ofN,N-dimethylformamide used was changed to 630 g. In result, 143.2 g ofdried crystals of tetrafluoroterephthalonitrile having a purity of 99.0%was prepared. The yield based on the tetrachloroterephthalonitrile was91.2%.

Example 4

[0071] Into a 20 L glass reactor, 2.40 Kg oftetrachloroterephthalonitrile having a purity of 98.35%, 2.34 Kg ofpotassium fluoride having an average bulk specific gravity of 0.5 g/mlprepared by the spray drying method and 5.43 Kg of N,N-dimethylformamidehaving a water content of 100 ppm as a solvent were charged, and whilestirring them with a stirrer having turbine blade, the temperature waselevated using an oil bath. During the reaction, because bulk solidmatters were adhered to the wall surface of the reactor, the reactionwas carefully carried out with occasionally changing the velocity of thestirring so that the bulk solid matters were not adhered to the utmost.From the time at which the internal temperature reached to 115° C., thereaction was continued for 4.5 hr. Thereafter, the reaction solution wascooled to 60° C., and transferred into a 20 L vessel. When estimatedfrom the mass of the reaction solution transferred, it was consideredthat the mass of bulk solid matters, which were adhered to the wallsurface of the reactor during the reaction and remained after thetransfer of the reaction solution, was about 1.01 Kg. (this masscorresponds to 9.9% of the all reaction solution mass) . After the allamount of the reaction solution was transferred, 11.63 Kg of water wasintroduced into the solution with stirring over 40 min, and thereby thepotassium chloride deposited were mostly dissolved and also crystals oftetrafluoroterephthalonitrile were deposited. The deposited crystalswere separated by a Nutsche funnel, and were washed with 2.28 Kg ofwater at 40° C. When analyzed by liquid chromatography and evaluated,the total amount of tetrafluoroterephthalonitrile present in thefiltrate filtered and the washing water was 0.002 Kg. (the amountcorresponds to 0.11% of the yield based ontetrachloroterephthalonitrile) . The resulting crystals were dried witha vacuum dryer at 60° C. to obtain 1.56 Kg of dried crystals. Whenanalyzed by gas chromatography, the crystals were found to betetrafluoroterephthalonitrile having a purity of 98.8%. The yield basedon the tetrachloroterephthalonitrile was 86.8%.

Example 5

[0072] Into a 2.5 m³ vertical screw-shaped (planetary-shaped) mixer, 420Kg of tetrachloroterephthalonitrile having a purity of 98.35%, 410 Kg ofpotassium fluoride having an average bulk specific gravity of 0.5 g/mlprepared by the spray drying method and 950 Kg of N,N-dimethylformamidehaving a water content of 100 ppm as a solvent were charged, and whilestirring them with a stirrer at 60-rotations per minute and 0.8revolution per minute in a nitrogen atmosphere, the temperature waselevated with passing steam at 3 Kg/cm² to a jacket. From the time atwhich the internal temperature reached to 115° C., the reaction wascontinued for 4.5 hr. Thereafter, the reaction solution was cooled to60° C., and transferred into a 3.5 m³ crystallization bath using aslurry pump. Just after the reaction solution was transferred, 2036 Kgof water was introduced over 40 min, and thereby the potassium chloridedeposited were mostly dissolved and also crystals oftetrafluoroterephthalonitrile were deposited. The deposited crystalswere separated by a centrifugal filter, and were washed with 400 Kg ofwater at 40° C. Thereafter the crystals were dried with a conical dryerto obtain 292.3 Kg of dried crystals. When analyzed by gaschromatography, the crystals were found to betetrafluoroterephthalonitrile having a purity of 99.0%. The yield basedon the tetrachloroterephthalonitrile was 93.1%.

Example 6

[0073] The procedure of Example 5 was repeated except that the amount ofN,N-dimethylformamide used was changed to 760 Kg. In result, 296.1 Kg ofdried crystals of tetrafluoroterephthalonitrile having a purity of 99.0%was prepared. The yield based on the tetrachloroterephthalonitrile was94.3%.

Comparative Example 1

[0074] Into a 20 L glass reactor, 2.03 Kg oftetrachloroterephthalonitrile having a purity of 98.35%, 2.62 Kg ofpotassium fluoride having an average bulk specific gravity of 0.5 g/mlprepared by the spray drying method and 14.16 Kg ofN,N-dimethylformamide having a water content of 100 ppm as a solventwere charged, and while stirring them with a stirrer having turbineblade, the temperature was elevated using an oil bath. From the time atwhich the internal temperature reached to 130° C., the reaction wascontinued for 5 hr. Thereafter, the reaction solution was introduced toa 50 L vessel containing 33.05 Kg of iced water. The potassium chloridedeposited were mostly dissolved and also crystals oftetrafluoroterephthalonitrile were deposited. The deposited crystalswere separated by a Nutsche funnel, and were washed with 1.73 Kg ofwater at 40° C. When analyzed by liquid chromatography and evaluated,the total amount of tetrafluorophthalonitrle present in the filtratefiltered and the washing water was 0.005 Kg. (the amount corresponds to0.3% of the yield based on tetrachloroterephthalonitrile). The resultingcrystals were dried with a vacuum dryer at 60° C. to obtain 1.22 Kg ofdried crystals. When analyzed by gas chromatography, the crystals werefound to be tetrafluoroterephthalonitrile having a purity of 99.0%. Theyield based on the tetrachloroterephthalonitrile was 80.4%.

1. A process for producing a fluorinated dicyanobenzene represented bythe formula (2):

wherein m is an integer of 1 to 4, n is 0 or an integer of 1 to 3, andm+n=4, which process comprises allowing a tetrachlorodicyanobenzenerepresented by the formula (1)

to react with a fluorinating agent in the presence of a non-protonicpolar solvent in an amount of from 0.1 to 3 times by mass based on saidtetrachlorodicyanobenzene.
 2. The process for producing a fluorinateddicyanobenzene according to claim 1, wherein the non-protonic polarsolvent is an organic solvent comprising at least one selected from thegroup consisting of N,N-dimethyl formamide, dimethyl sulfoxide andN-methyl-2-pyrrolidone.
 3. The process for producing a fluorinateddicyanobenzene according to claim 1, wherein the non-protonic polarsolvent is N,N-dimethyl formamide.
 4. The process for producing afluorinated dicyanobenzene according to any one of claims 1 to 3,wherein the fluorinating agent is an alkali metal fluoride or alkalineearth metal fluoride.
 5. The process for producing a fluorinateddicyanobenzene according to claim 4, wherein the fluorinating agent ispotassium fluoride.
 6. The process for producing a fluorinateddicyanobenzene according to claim 5, wherein said potassium fluoride isprepared by a spray drying method.
 7. The process for producing afluorinated dicyanobenzene according to claim 5 or 6, wherein saidpotassium fluoride has an average bulk specific gravity of from 0.1 to0.7 g/ml.
 8. The process for producing a fluorinated dicyanobenzeneaccording to any one of claims 1 to 7, wherein the fluorinateddicyanobenzene represented by the formula (2) is tetrafluorophthalonitrile, tetrafluoro isophthalonitrile or tetrafluoroterephthalonitrile.
 9. The process for producing a fluorinateddicyanobenzene according to claim 8, wherein the fluorinateddicyanobenzene represented by the formula (2) istetrafluoroterephthalonitrile.
 10. The process for producing afluorinated dicyanobenzene according to any one of claims 1 to 9, whichprocess comprises carrying out the reaction while disintegrating bulksolid matters contained in a reaction mixture and/or while removing bulksolid matters adhered to a wall inside a reaction vessel.
 11. Theprocess for producing a fluorinated dicyanobenzene according to claim10, wherein, in carrying out the reaction while disintegrating bulksolid matters contained in the reaction mixture and/or while removingbulk solid matters adhered to the wall inside the reaction vessel, amixing machine equipped with a ribbon-shaped and/or screw-shaped stirreris used.
 12. The process for producing a fluorinated dicyanobenzeneaccording to claim 10, wherein, in carrying out the reaction whiledisintegrating bulk solid matters contained in the reaction mixtureand/or while removing the bulk solid matters adhered to the wall insidethe reaction vessel, any one device of a kneader mixer, internal mixer,muller mixer, crusher, ribbon-shaped mixer, vertical screw-shaped(planetary-shaped) mixer and rotary mixer is used.
 13. The process forproducing a fluorinated dicyanobenzene according to any one of claims 10to 12, wherein the bulk solid matters are in an amount of not more than10% by mass based on the total amount of the reaction mixture incarrying out the reaction.
 14. The process for producing a fluorinateddicyanobenzene according to any one of claims 1 to 13, wherein thereaction temperature is between 80° C. and 200° C.
 15. A process forproducing a fluorinated dicyanobenzene, which process comprises thesteps of conducting a fluorinating reaction by the process as claimed inany one of claims 1 to 14, thereafter cooling a reaction solution tolower than 60° C. and adding water to crystallize and deposit afluorinated dicyanobenzene represented by the formula (2).